1. Field of Invention
The invention relates to a copying system including a host device, such as a personal computer, and a peripheral device connected to each other. Specially, the invention relates to a copying system capable of performing a copying processing for a color original document within a short time, even when the available memory in the peripheral device is limited.
2. Description of Related Art
As shown in a block diagram of FIG. 10, a copying system is conventionally comprised of a multi-function center (hereinafter referred to as MFC) 100 and a personal computer 200 (hereinafter referred to as PC), as a host device connected to each other.
Color images on an original document are read by a scanner 101 of the MFC 100 as analog data of three colors red, green, and blue. Hereinafter, red, green, and blue are referred to as “R”, “G”, and “B”, respectively. The analog RGB data is converted by a control circuit 102 into multi-value 8-bit digital RGB data, and is transmitted to the PC 200 (104). The multi-value RGB data transmitted to the PC 200 is received via a TWAIN driver 201. Thereafter, the multi-value RGB data is subjected to a color matching processing 202, and is output to a color copying application 203. The multi-value RGB data underwent the color matching processing 202 and output to the color copying application 203, is then output to a printer driver 204, as the copying designation by an operator. Further, the multi-value RGB data is converted by the printer driver 204 into 1-bit binary data of four colors of cyan, magenta, yellow, and black, that can be printed in a printer 103 of the MFC 100. Hereinafter, cyan, magenta, yellow, and black are referred to as “C”, “M”, “Y”, and “K”, respectively. The binary CMYK data is then transmitted to the MFC 100 (205). The binary CMYK data transmitted to the MFC 100 is output from the control circuit 102 to the printer 103. The printer 103 performs color printing. FIG. 11 shows a manner when three copies of a total of two pages of original documents are produced in the sort copying mode, according to the designation by an operator.
The amount of image data of a color original document is large. For example, the amount of the image data for a A4-sized color original document will be approximately 10 Mbyte. A peripheral device of the MFC 100 has a memory therein whose size is not so large that the available memory will be limited. The PC 200 usually has a large-capacity memory. Therefore, by constructing the above-described color copying system in the following manner, the color copying processing can be smoothly performed. The color image data obtained by reading a color original document by the scanner 101 of the MFC 100 is transmitted to the PC 200 and is temporarily stored therein. The data is sorted in the PC 200, and is then sent back to the MFC 100. The data sent back from the PC 200 is printed in color by the printer 103 of the MFC 100. With the above-described construction, the color copying processing for the color original document with the large amount of image data, can be smoothly performed in the MFC 100, via the PC 200, by using the memory in the PC 200, even though the memory size in the MFC 100 is limited.
However, in the above-described color copying system, the multi-value RGB data has to undergo the color matching processing 202 and then has to be converted into the binary CMYK data by the printer driver 204 in the PC 200. These steps lead to the longer color copying processing time. In addition, the multi-value RGB data is larger in size, as compared with the binary CMYK data. Therefore, it takes time to send such large multi-value RGB data in size from the MFC 100 to the PC 200.
The color matching processing 202 is a collection processing performed for the multi-value RGB data on a pixel basis according to a display driver of the PC 200, to show the images on a display in the PC 200. The color matching processing 202 requires a relatively long time, though this is unnecessary for color printing. That is, the color matching processing 202 is not needed in the case where an operator does not require the indication of the images on the display but requires the color copy thereof. To the contrary, the conversion of the multi-value RGB data into the binary CYMK data is necessary for color printing, and is performed by the printer driver 204 as described above. However, as shown in FIG. 11, the printer driver 204 has to convert the multi-value RGB data into the binary CMYK data for the total of six pages (2 pages X 3 copies), even though the original document is only two pages, as the operator designates the three copies of a total of two pages of the original documents. This also leads to the longer color copying processing time.